1. Field of the Invention
This invention relates to a magnetic recording media dispersants and more particularly to reactive dispersants for magnetic particles in the coating of magnetic media such as tapes, cassettes and the like.
2. Description of the Prior Art
Magnetic recording media products such as magnetic tapes, reels, cassettes, cartridges, flexible disks and cards have been developed for information storage, logging, dictation, entertainment and other applications. Magnetic tape has become the principal recording medium for information storage because it is permanent, versatile, erasable, reusable and high capacity.
The two basic components in a magnetic recording medium are a non-magnetic support or substrate and a coating on the support which contains finely divided magnetic particles. Polyethylene terephthalate, a polyester, is the most commonly used support. The coating on the support is usually composed of fine particles of a ferri-magnetic material embedded in a matrix of organic polymer.
Manufacture of magnetic tape involves formulating a coating composition, dispersing magnetic particles in the composition, preparing a support, coating the support with the composition, orienting the particles, drying, curing, testing and packaging.
For a magnetic tape to perform, the magnetic particles must be thoroughly and completely dispersed in the coating composition. The dispersant aids in deagglomeration of the magnetic particles. Individual particles should be separated to the maximum possible degree because tape performance depends on dispersion.
U.S. Pat. No. 3,144,352--Talley, issued Aug. 11, 1964, describes use of lecithin as the dispersant for magnetic particles in a coating composition for magnetic tape. Lecithin is one of the most common dispersants. Lead naphthenate, calcium naphthenate and N-alkyl trimethylenediamines are also used as dispersants.
U.S. Pat. No. 3,647,539--Weber, issued Mar. 7, 1972, describes use of a tri lower alkyl polypropyleneoxy quaternary ammonium compound as the dispersant in a coating composition containing magnetic pigments such as gamma ferric oxide with carbon particles in a liquid binder resin.
U.S. Pat. No. 4,556,604--Ohbayashi et al, issued Dec. 3, 1985 describe use of a phosphate ester (GAFAC RE-610, a free acid of a complex organic phosphate ester having an aromatic hydrophobe base and not known to copolymerize under ultraviolet or electron beam radiation) in a coating composition referred to as a magnetic paint for magnetic tape.